import com.sun.source.tree.Tree;

public class BinarySearchTree {
    static class TreeNode {
        public int val;
        public TreeNode left;
        public TreeNode right;

        public TreeNode(int val) {
            this.val = val;
        }
    }

    //查询
    public TreeNode root = null;

    public TreeNode search(int k) {
        TreeNode cur = root;
        while (cur != null) {
            if (cur.val > k) {
                cur = cur.right;
            } else if (cur.val < k) {
                cur = cur.left;
            } else {
                return cur;
            }
        }
        return null;
    }

    //插入
    public void insert(int val) {
        TreeNode node = new TreeNode(val);
        if (root == null) {
            root = node;
            return;
        }
        TreeNode cur = root;
        TreeNode parent = null;
        while (cur != null) {
            if (cur.val < val) {
                parent = cur;
                cur = cur.right;
            } else if (cur.val > val) {
                parent = cur;
                cur = cur.left;
            } else {
                return;
            }
        }
        //parent 指向的节点 就是需要插入的节点位置 父节点
        if (parent.val > val) {
            parent.left = node;
        } else {
            parent.right = node;
        }
    }

    //删除
    public void remove(int key) {
        TreeNode parent = null;
        TreeNode cur = root;
        while (cur != null) {
            if (cur.val < key) {
                parent = cur;
                cur = cur.right;
            } else if (cur.val > key) {
                parent = cur;
                cur = cur.left;
            } else {
                removeNode(parent, cur);
                return;
            }
        }
    }

    private void removeNode(TreeNode parent, TreeNode cur) {
        if (cur.left == null) {
            if (cur == root) {
                root = cur.right;
            } else if (cur == parent.left) {
                parent.left = cur.right;
            } else {
                parent.right = cur.right;
            }
        } else if (cur.right == null) {
            if (cur == root) {
                root = cur.left;
            }
            if (cur == parent.left) {
                parent.left = cur.left;
            } else {
                parent.right = cur.left;
            }
        } else {
            TreeNode target = cur.right;
            TreeNode targetP = cur;
            while (target.left != null) {
                targetP = target;
                target = target.left;
            }
            cur.val = target.val;
            if (target == target.left) {
                targetP.left = target.right;
            } else {
                targetP.right = target.right;
            }
        }
    }
}
